Radioimmunoassay of a glycoprotein associated with malignancy

A glycoprotein associated with malignancy was purified from the 0.6M perchloric acid-soluble fraction of serum obtained from cancer patients. The purified glycoprotein contained sialic acid, which was responsible for binding to wheat-germ agglutinin-Sepharose. Gel electrophoresis showed one band with an apparent Mr of 50 000-55 000, and the isoelectric point was 4.4 +/- 0.1. The glycoprotein could be distinguished from carcinoembryonic antigen and alpha-fetoprotein. Iodination of this material with chloramine-T permitted development of a radioimmunoassay.